Remove @SystemApi from the fields of R.styleable (part 2)

Fix fields missed by previous change
Ica8cdcc7bbb40b4476c39db247d744f5e870cd06.

Bug: 67891551
Test: m -j checkapi does not report an error and cts/tests/signature/runSignatureTests.sh
Change-Id: I1a7b4a68fff6883085d420a41ad1f30bf03ffad5